1. Field of the Invention
The present invention relates to a radiographic diagnostic device with a projection unit formed as a computed tomography system with a radiation emitter and a line detector, which can be moved jointly about a projection area, and with a support apparatus for an examination subject that has a support plate.
2. Description of the Prior Art
A radiographic diagnostic device of this type is known from U.S. Pat. No. 5,639,419, for example. In this computed tomography device, a frame, known as a gantry, is provided, which carries a rotatably mounted projection unit consisting of a radiation emitter and a line-shaped radiation detector arranged opposite one another for transirradiating an examination area under different projections. Furthermore, a support apparatus with a displaceable support plate is allocated to the computed tomography device, on which an examination subject is supported and can be moved into the examining area. To this end, the support plate is mounted such that it can be displaced at least along its longitudinal axis. In the examining area, which is formed by a central, generally circular tunnel-like opening of the gantry, a radiation examination of the subject can be conducted by actuating the projection unit to emit radiation while rotating around the examination subject, and the signals of the line-shaped radiation detector are read out. The output signals that can be derived from the line-shaped radiation detector are fed to a computer, which generates image signals from them, which can be rendered on a display device. With such a computed tomography device, cross-sectional projections of an examination subject are obtained. It is also possible to displace the support plate with the examination subject thereon in the examining area along the longitudinal axis of the support plate while emitting radiation with the projection unit remaining stationary, so that it is also possible to create survey projections. In the computing unit, the cross-sectional projections can be combined into a volume projection in known fashion, so that it is possible to display the examination area in three dimensions. Such a representation is also possible by means of a spiral scan of the examination area, wherein the support plate with the examination subject is moved, preferably continuously, along the longitudinal axis of the support plate during the rotating radiation scan. For the radiation scan of the examination subject as described above, the radiation beam emanating from the radiation emitter is limited by a diaphragm into a narrow radiation fan and is incident on the line-shaped radiation detector, which has a frontally attached radiation diaphragm.